When I go to the login page for twitter (which I have to do MANY times a day because I have my personal account and my website account), I enter my username, and then tab to get to the password. On 99% of websites, one tab is all it takes to do username -> password. However, on twitter, it takes 2, because it tabs through the “forgot your username” link first.

99% of people tabbing from username to the next field are going to be tabbing from username to password, so we should support this workflow in a one tab fashion to save people the frustration of entering their password without realizing they’re not even tabbed over to that field.